The present invention relates to 3-cyano-2,4,5-trifluoro-benzoyl fluoride, to a process for its preparation, and to other novel halogenobenzene derivatives as intermediates.
3-Cyano-2,4,5-trifluoro-benzoyl chloride can be used for the preparation of antiinfective quinolonecarboxylic acids (cf. DE-A 1 963 805 No.19 606 762.6=WO 97/31001). The preparation starts from 2,4-dichloro-5-fluoro-3-cyanobenzoic acid and leads by a known method (cf. DE 3702393 A1) to 2,4-dichloro-3-cyano-5-fluoro-benzoyl chloride, which is then fluorinated. A disadvantage of this process is, in particular, the Sandmeyer reaction, which proceeds with poorly reproducible yield, using a molar amount of copper cyanide and an additional three-fold excess of sodium cyanide to give 2,4-dichloro-3-cyano-5-fluoro-benzoic acid. The use of such large amounts of cyanide also harbours a considerable hazard potential when the reaction is carried out industrially.
The present invention relates to novel 3-cyano-2,4,5-trifluoro-benzoyl fluoride of the formula (I) 
The invention also relates to a process for the preparation of 3-cyano-2,4,5-trifluoro-benzoyl chloride by chlorination of 3-cyano-2,4,5-trifluoro-benzoyl fluoride.
In addition, the invention also relates to the use of 3-cyano-2,4,5-trifluoro-benzoyl fluoride for the synthesis of quinolones.
The invention further relates to a multistage process for the preparation of 3-cyano-2,4,5-trifluoro-benzoyl fluoride, which starts from 5-fluoro-1,3-xylene (VIII), characterized in that 5-fluoro-1,3-xylene (VIII) is bichlorinated in the ring in the presence of a catalyst under ionic conditions to give 2,4-dichloro-5-fluoro-1,3-dimethylbenzene (VII), which is then chlorinated in the side chains under free-radical conditions to give 2,4-dichloro-5-fluoro-3-dichloromethyl-1-trichloromethylbenzene (VI), which is hydrolysed via 2,4-dichloro-5-fluoro-3-dichloromethylbenzoic acid (V), which can be isolated if necessary, to give 2,4-dichloro-5-fluoro-3-formyl-benzoic acid (IV), the aldehyde group of which is reacted to give 2,4-dichloro-5-fluoro-3-N-hydroxyiminomethyl-benzoic acid (III), from which, with simultaneous conversion of the carboxyl group into the chlorocarbonyl group, water is eliminated using an acid chloride to give the nitrile 2,4-dichloro-3-cyano-5-fluoro-benzoyl chloride (II), which, finally, is subjected to fluorine/chlorine exchange. 
Alternatively, 2,4-dichloro-5-fluoro-3-formyl-benzoic acid (IV) can also be reacted to give 2,4-dichloro-5-fluoro-3-cyano-benzoic acid (IX), which can then be converted into the acid chloride (II). 
The intermediates of the formulae (III) to (VII) are novel without exception and are likewise provided by the invention.
3-Cyano-2,4,5-trifluoro-benzoyl fluoride is an intermediate, readily obtainable by the process described here, for the preparation of 3-cyano-2,4,5-trifluoro-benzoyl chloride.
The process according to the invention is described in more detail below.
The ring chlorination of commercially available 5-fluoro-1,3-xylene (VIII) to give 2,4-dichloro-5-fluoro-1,3-dimethylbenzene (VII) is carried out using chlorine gas. 
2,4-Dichloro-5-fluoro-1,3-dimethylbenzene (VII) is novel.
The catalyst used is one or more Friedel-Crafts catalysts, preferably a Lewis acid, such as, for example, iron (III) chloride or aluminium chloride. For example, from 0.1 to 10 mol %, preferably from 0.2 to 2 mol %, based on 5-fluoro-1,3-xylene, are used.
The reaction can be carried out at temperatures below room temperature or at slightly elevated temperature. Preference is given to temperatures between 0 and 40xc2x0 C.
The chlorination can be carried out without a diluent or in a suitable inert diluent. Particularly suitable diluents are halogenated hydrocarbons such as dichloro-, trichloro-, tetrachloromethane, 1,2-dichloroethane or 1,2,4-trichlorobenzene. The chlorination can be carried out continuously or batchwise. In a continuous process, it is wise to proceed only to a low conversion because the chlorination does not take place with complete selectivity. In the batchwise procedure, chlorine is introduced in an amount up to approximately 0.8-1.1 times, preferably 0.8-0.95 times, the theoretical amount, the reaction mixture achieving a solid consistency in the chlorination without diluent. It is also advantageous in this connection to proceed only up to this not-too-high conversion because then the losses as a result of superchlorination on the one hand and the space-time yield on the other are in an optimum range.
The mixture is worked up, for example, by fractional distillation. It is advantageous to return recovered starting material and monochlorinated compounds to the process.
The side-chain chlorination of 2,4-dichloro-5-fluoro-1,3-dimethylbenzene (VII) to give 2,4-dichloro-5-fluoro-3-dichloromethyl-1-trichloromethylbenzene (VI) is preferably carried out without a diluent using chlorine gas. 
2,4-Dichloro-5-fluoro-3-dichloromethyl-1-trichloromethylbenzene (VI) is novel.
The conditions for the free-radical reaction are achieved by elevated temperature and optional irradiation with a light source or addition of a customary free-radical initiator. Suitable light sources are incandescent lamps such as, preferably, halogen lamps or medium- or high-pressure mercury vapour lamps. Suitable free-radical initiators are, for example, benzoyl peroxide, di-tert-butyl peroxide or 2,2-azobis(isobutteronitrile) (AIBN). The reaction temperature can be between 80 and 200xc2x0 C., preferably 100 and 180xc2x0 C., particularly preferably between 120 and 170xc2x0 C.
The chlorination can be carried out continuously or batchwise. In a continuous process, it is wise to proceed only up to a low conversion because the chlorination does not take place with complete selectivity. In the batchwise procedure, chlorine is introduced in an amount up to approximately 0.8-1.2 times, preferably 0.95-1.15 times the theoretical amount, corresponding to from 40 to 75%, preferably from 65 to 75%, conversion to the desired product.
The reaction mixture can be worked up, for example, by fractional distillation or recrystallization from a suitable solvent such as, for example, methanol. Preference is given to distillation. Insufficiently chlorinated compounds can be introduced again into the chlorination.
The chlorinated side chains are hydrolysed using a protic acid, optionally in the presence of water. Suitable protic acids are mineral acids such as, for example, sulphuric acid, hydrochloric acid or phosphoric acid, and organic acids such as, for example, formic acid, acetic acid or oxalic acid, and mixtures thereof and with a protic solvent such as, for example, water. 
Depending on the type, concentration and amount of acid and reaction temperature, it is possible to carry out the hydrolysis of 2,4-dichloro-5-fluoro-3-dichloromethyl-1-trichloromethylbenzene (VI) to give 2,4-dichloro-5-fluoro-3-formyl-benzoic acid (IV) in one or two steps. Because the trichloromethyl group is hydrolysed significantly more quickly, 2,4-dichloro-5-fluoro-3-dichloromethylbenzoic acid (V) can, if the reaction conditions are suitable, be isolated directly and converted to (IV) in a further hydrolysis step. As far as the overall process of the preparation of 3-cyano-2,4,5-trifluoro-benzoyl fluoride according to the invention is concerned, it is advantageous to carry out the hydrolysis in one step.
2,4-Dichloro-5-fluoro-3-formyl-benzoic acid (IV) and 2,4-dichloro-5-fluoro-3-dichloromethylbenzoic acid (V) are novel.
The amount of protic acid is unimportant. The acid, for example, is initially introduced and the molten aromatic compound (VI) or (V) is added. Preference is given to using sufficient acid (mixture) for the reaction mixture to remain stirrable.
The temperature for the hydrolysis can be varied within a wide range depending on the desired product, acid and reaction time. The temperature is generally from 0 to 100xc2x0 C.
The product can be isolated, for example, by precipitation with water and removal by filtration or extraction.
The oxime (III) is prepared from 2,4-dichloro-5-fluoro-3-formyl-benzoic acid (IV) by a generally known method. 
2,4-Dichloro-5-fluoro-3-N-hydroxyiminomethyl-benzoic acid (III) is novel.
The reagent used is a salt of hydroxylamine such as, for example, the hydrochloride or sulphate, or also the free base.
If a salt of hydroxylamine is used, the reaction is carried out in the presence of an acid acceptor. Suitable acid acceptors are customary inorganic or organic bases. These include, preferably, the hydroxides, alkoxides, acetates, carbonates and hydrogen carbonates of alkaline earth metals or alkali metals, such as, for example, the hydroxides of sodium, potassium or ammonium, sodium methoxide, sodium ethoxide, potassium tert-butoxide, the acetates of sodium, potassium, calcium or ammonium, the carbonate of sodium, potassium or ammonium, the hydrogen carbonates of sodium or potassium, and tertiary amines, such as trimethylamine, triethylamine, tributylamine, N,N-dimethlylaniline, N,N-dimethyl-benzylamine, pyridine, N-methylpiperidine, N-methylmorpholine, N,N-dimethylaminopyridine, diazabicyclooctane (DABCO), diazabicyclononene (DBN) or diazabicycloundecene (DBU).
The reaction is carried out in the presence of a diluent. Suitable diluents are water, organic solvents and any mixtures thereof. Examples which may he mentioned are ethers, such as diethyl ether, diisopropyl ether, methyl t-butyl ether, methyl t-amyl ether, dioxane, tetrahydrofuran, 1,2-dimethoxyethane, 1,2-diethoxyethane, diethylene glycol dimethyl ether or anisole; nitrites, such as acetonitrile, propionitrile, n- or i-butyronitrile; alcohols, such as methanol, ethanol, n- or i-propanol, n-, iso-, sec- or tert-butanol, ethanediol, propane-1,2-diol, ethoxyethanol, methoxyethanol, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether; water.
The temperature for the reaction can be varied within a relatively wide range. It is generally chosen to be between 10 and 100xc2x0 C., preferably between 20 and 80xc2x0 C.
Per mol of formylbenzoic acid (IV), from 1 to 1.5 equivalents of hydroxylamine (salt) are used, and from 200 to 2000 ml, preferably from 500 to 1000 ml, of diluent are used. Per equivalent of hydroxylamine, from 1 to 5, preferably from 1.1 to 3, equivalents of acid acceptor are used.
For work-up, the reaction mixture is acidified, for example using a mineral acid, and, where appropriate, the product is extracted using a suitable solvent such as, for example, methyl tert-butyl ether, or the solid is filtered off.
If the reaction of (IV) with hydroxylamine or a salt of hydroxylamine is carried out in the presence of formic acid, then the reaction product obtained is the nitrile (IX). Preference is given to using hydroxylamine hydrochloride.
The reaction can be carried out in the presence of a diluent. Suitable diluents are water, organic solvents and any mixtures thereof. Preferably, the reaction is carried out in from 85% to 98% strength aqueous formic acid.
The temperature of the reaction can be varied in a relatively wide range. It is generally chosen to be between 10 and 120xc2x0 C., preferably between 50 and 110xc2x0 C.
Per mol of (IV), from 1 to 1.5 equivalents of hydroxylamine (salt) are used, and from 100 to 3000 ml, preferably from 500 to 1500 ml, of aqueous formic acid are used.
The starting materials can be added in different orders. For example, all of the starting materials can be initially introduced and then heated up to the reaction temperature together. It is, however, also possible to initially introduce the hydroxylamine (salt) into the aqueous formic acid, and introduce the starting material (IV) at the reaction temperature.
Alternatively, the starting material (IV), which can also be used moistened with sulphuric acid, can be introduced into the aqueous formic acid, and the hydroxylamine (salt) or a solution of the hydroxylamine (salt) in water or aqueous formic acid can be metered in at the reaction temperature.
For work-up, the mixture is further diluted with water, and (IX) is filtered off as solid.
3-Cyano-2,4-dichloro-5-fluorobenzoic acid (IX) is converted into benzoyl chloride (II) using a chlorinating agent as reagent.
Suitable chlorinating agents are those agents given below under the reaction conditions stated there.
The preparation of 2,4-dichloro-3-cyano-5-fluoro-benzoyl chloride (II) by elimination of water from 2,4-dichloro-5-fluoro-3-N-hydroxyiminomethyl-benzoic acid (III) with simultaneous conversion of the carboxylic acid function into the carbonyl chloride takes place using a chlorinating agent as reagent. 
Suitable chlorinating agents are inorganic or organic acid chlorides, such as, for example, phosgene (carbonyl dichloride) or the synthetic equivalents trichloromethyl chloroformate or bis(trichloromethyl) carbonate, oxalyl chloride, acetyl chloride, thionyl chloride, sulphuryl chloride, phosphorous trichloride, phosphorous pentachloride or phosphorous oxychloride and mixtures thereof. Preference is given to phosgene or thionyl chloride.
The reaction can be carried out in the presence or absence of a suitable diluent. Suitable diluents for this purpose are organic solvents, an acid chloride which is liquid under the reaction conditions, i.e. the reagent itself, and any mixtures thereof. Examples of organic solvents which may be mentioned are: aliphatic, alicyclic or aromatic hydrocarbons, such as, for example, petroleum ether, hexane, heptane, cyclohexane, methylcyclohexane, benzene, toluene, xylene or decalin; halogenated hydrocarbons, such as, for example, chlorobenzene, dichlorobenzene, methylene chloride, chloroform, tetrachloromethane, dichloroethane, trichloroethane or tetrachloroethylene; ethers, such as diethyl ether, diisopropyl ether, methyl t-butyl ether, methyl t-amyl ether, dioxane, tetrahydrofuran, 1,2-dimethoxyethane, 1,2-diethoxyethane, diethylene glycol dimethyl ether or anisole.
The oxime compound and chlorinating agent can be added in any order. In a preferred embodiment, the solvent-free reagent is initially introduced, and 2,4-dichloro-5-fluoro-3-N-hydroxyiminomethyl-benzoic acid is metered in continuously or in portions at a rate of controllable gas evolution (hydrogen chloride and in some cases other gases such as carbon dioxide or sulphur dioxide).
From 2 to 10 mol of acid chloride are generally used per mol of compound (III). It is also possible to use a larger excess, particularly when the acid chloride also serves as diluent.
The temperature in the reaction can be varied in a relatively wide range. It is generally chosen to be between 0 and 150xc2x0 C., preferably between 30xc2x0 C. and boiling temperature. The process is generally carried out under atmospheric pressure. It is also possible to carry out the reaction under reduced or elevated pressure. For example, when phosgene is used, it is wise to keep it liquid at a temperature above the boiling point at atmospheric pressure and to release the gases which are liberated by means of a pressure-relief device.
The mixture can be worked up, for example, by fractional distillation.
The final fluorine/chlorine exchange takes place nucleophilically using a fluoride source. 
Suitable fluoride sources are, for example, metal fluorides, preferably alkali metal fluorides, such as, for example, potassium fluoride or caesiuim fluoride.
The fluorination is carried out in the presence of a diluent. Suitable diluents are polar aprotic solvents such as, for example, amides, such as N,N-dimethylformamide, N,N-dimethylacetamide, N-methylformanilide, N-methylpyrrolidone or hexamethyl-phosphoramide; ureas, such as N,N-dimethylpropyleneurea, N,N-dimethylethyleneurea; sulphoxides, such as dimethyl sulphoxide; sulphones, such as sulpholane.
The fluorination can also be carried out in the presence of known catalysts for halex reactions.
Per mol of 2,4-dichloro-3-cyano-5-fluoro-benzoyl chloride, from 3 to 10 mol, preferably from 3.4 to 8 mol, particularly preferably from 3.7 to 6 mol of fluoride are used.
The fluorination is carried out at elevated temperature. The temperature is generally from 100 to 250xc2x0 C., preferably from 130 to 200xc2x0 C.
Work-up can, for example, involve distillation of the product under reduced pressure, or extraction using a solvent and subsequent fractional distillation.
The preparation of 3-cyano-2,4,5-trifluoro-benzoyl chloride from 3-cyano-2,4,5-trifluoro-benzoyl fluoride (I) according to the invention is carried out analogously to known processes for the rechlorination of carbonyl fluorides. Reagents which are suitable for this purpose are silicon chlorides, such as, for example, silicon tetrachloride, trimethylchlorosilane or dimethyldichlorosilane; or calcium chloride, in each case in the presence of catalytic amounts of a Lewis acid, such as, for example, aluminium chloride or boron trichloride; or said or other chlorine-containing Lewis acids themselves.
Per mol of compound (I), from 1 to 2 equivalents of reagent and, where appropriate, from 0.01 to 0.1 mol of Lewis acid are generally used.
The temperature in the reaction can be varied within a relatively wide range. The reaction is generally carried out at from 20 to 150xc2x0 C. when silicon chlorides and Lewis acids are used, and at from 120 to 200xc2x0 C. when calcium chloride is used.
Work-up is preferably by vacuum distillation.
It is extremely surprising that the ring chlorination of 5-fluoro-1,3-xylene to give 2,4-dichloro-5-fluoro-1,3-dimethylbenzene proceeds with very high selectivity, without which the synthesis sequence according to the invention would not be possible.
Further details of the processes are given in the examples below, without the invention being limited thereby.